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Chapter 1

EESB05H3 Chapter Notes - Chapter 1: Soil Horizon, Helminthiasis, Regolith


Department
Environmental Science
Course Code
EESB05H3
Professor
Marney Isaac
Chapter
1

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EESB05
Chapter 1: The Soils Around Us
- Soils play 6 key roles
SOILS AS MEDIA FOR PLANT GROWTH
- Provide a medium for plant roots and supply nutrient elements
- Properties of soil determines the nature of the vegetation present
- Properties of soil indirectly determines the number and types of animals and people that can be
supported
- Shoots are plant leaves, flowers, stems, and limbs
- Roots are underground and have many functions in which the plant obtains from the soil
1) Physical Support
- Soil mass anchors the root system so that the plant does not fall over or blow away
2) Air
- Process of respiration to obtain energy
- Roots produce CO2 and uses O2 in its ventilation process through soil pores
3) Water
- Soil pores absorb rainwater and hold it where it can be used by plant roots
- Plants require a continuous stream of water to use in cooling, nutrient transport, turgor
maintenance, and photosynthesis
- Rainfall varies from place to place, and deep soils may store enough water for plants to survive
long periods without rain
4) Temperature moderation
- Insulating properties of soil protect root system from extremes of hot and cold that occur at the
soil surface
5) Protection from toxins
- Phytotoxic substances are chemicals that are toxic to plants, produced by human activity, plant
roots, microorganisms, or by natural chemical reactions
- Soils protect plants from these toxic substances by ventilating gases, decomposing or adsorbing
organic toxins, or suppressing toxin-producing organisms

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6) Nutrient Elements
- Soil supply plants with mineral nutrients
- Fertile soil provide continuing supply of dissolved mineral nutrients for optimal plant growth
Ex. Metallic elements such as potassium, calcium, iron, copper, etc. and non-metallic elements
such as nitrogen, sulphur, phosphorus, and boron
Essential elements chemical elements required for normal plant growth
- There are 92 naturally occurring chemical elements, but only 17 are essential elements
Geophagy the practice of eating soil deliberately, a widespread practice in some societies
Ex. Thailand, Uganda, Turkey, rural Alabama
- Benefits vary such as gaining iron, calcium, etc.
- Drawbacks include parasitic worm infection, lead poisoning, mineral nutrient imbalances, etc.
SOIL AS REGULATOR OF WATER SUPPLIES
- The nature and management of soils has a major influence on the purity and the amount of
water that end up in aquatic systems
- Rainwater travels through soil or flow over its surface at some point before reaching aquatic
systems
- Water can be soaked by soil and stored, while some will seep through to the groundwater
- Water is purified through the upper layers of soil, which removes impurities or kills disease
organisms
- If soil is shallow or impermeable, then surface flowing water will pick up debris and can cause
a flash flood of muddy water
SOIL AS RECYCLER OF RAW MATERIALS
- Recycling a vital process in ecosystems (forests, farms, cities, etc.)
- Soil plays an important role in geochemical cycles, by assimilating great quantities of organic
waste and turning it into beneficial humus
- Humus is stable organic matter that cannot be broken down any further
- Minerals have been converted into forms that can be utilized by plants and animals, and carbon
returned to the atmosphere as carbon dioxide
SOIL AS MODIFIER OF THE ATMOSPHERE
- Soil interacts in many ways with the air and atmosphere
- Dry, poorly structured, and unvegetated soils contribute dust particles to the atmosphere
- Evaporation of soil moisture contributes water vapour in the atmosphere, which alters
temperature, composition, and weather patterns
- Soils can absorb gases (such as oxygen and methane) and release gases (such as carbon dioxide
and nitrous oxide), which can influence atmosphere composition and global warming

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SOIL AS HABITAT FOR SOIL ORGANISMS
- The most complex and diverse ecosystems on Earth are underground
- Soil is home to a diversity of organisms where they interact
SOIL AS ENGINEERING MEDIUM
- Soil is one of the earliest and most widely used building materials
Ex. African mud huts, cement-stabilized buildings, etc.
- Some soils are a good base on which to build roads and structures, while others are not as stable
PEDOSPHERE AS ENVIRONMENTAL INTERFACE
- The soil acts as an interface between rock (lithosphere), air (atmosphere), water
(hydrosphere), and living things (biosphere)
Pedosphere a conceptual zone within the ecosystem consisting of soil bodies
- There are different functions and interfacing at different levels and scales
Ex. Soils channel water from bedrock to the oceans (scale of kilometres)
SOIL AS A NATURAL BODY
- Soil is referred to as “material” or as “natural bodies
- It is a material composed of minerals, gases, water, organic substances, and microorganisms
- Soil is a three-dimensional natural body that covers the Earth, but is highly variable from
place to place
- Soils are natural bodies composed of soil, roots, animals, rocks, artifacts, etc.
Regolith an unconsolidated layer of weathered rock and soil material above solid rock
- Regolith material has been transported from other areas, therefore all or part of the regolith may
not be related to the rock now found below it
Saprolite soft weathered bedrock that retains the fabric and structure of the parent rock, but is
porous and loose enough to be dug with a spade
- Soil is the product of destructive and creative (synthetic) processes that form contrasting layers
called soil horizons
Pedology the study of soils as natural bodies, the properties of soil horizons, and relationships
among soils within a landscape]
Edaphologists soil scientists that focus on the soil as habitat for living things especially plants
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